pipicpowerd.c add time out to WiFi up checking

The state of the WiFi connection is checked at time intervals defined by
WIFINT in the configuration file. If the connection is down the total
down time is summed up until it exceeds the WIFITIMEOUT in the configuration
file. In this case following actions are possible:

WIFIACT
0        do nothing
1        bring down the wlan0 interface and bring it up again
2        reboot Raspberry Pi
3        power cycle Raspberry Pi